Lithium containing nanofibers

ABSTRACT

Lithium-containing nanofibers, as well as processes for making the same, are disclosed herein. In some embodiments described herein, using high throughput (e.g., gas assisted and/or water based) electrospinning processes produce nanofibers of high energy capacity materials with continuous lithium-containing matrices or discrete crystal domains.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application Nos.61/605,937, filed Mar. 2, 2012, and 61/701,854, filed Sep. 17, 2012,both of which are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

Batteries comprise one or more electrochemical cell, such cellsgenerally comprising a cathode, an anode and an electrolyte. Lithium ionbatteries are high energy density batteries that are fairly commonlyused in consumer electronics and electric vehicles. In lithium ionbatteries, lithium ions generally move from the negative electrode tothe positive electrode during discharge and vice versa when charging. Inthe as-fabricated and discharged state, lithium ion batteries oftencomprise a lithium alloy/compound (such as a lithium metal oxide) at thecathode (positive electrode) and another material, such as carbon, atthe anode (negative electrode).

SUMMARY OF THE INVENTION

Provided in certain embodiments herein are nanofibers comprising alithium material. In some embodiments, the nanofibers comprise acontinuous matrix or backbone of the lithium material (e.g., does notcomprise lithium-containing-nanoparticles or otherlithium-containing-domains on or in another continuous matrix material).In specific embodiments, the lithium-containing-continuous matrix orbackbone comprises a core matrix material (e.g., the lithium material isnot coated on another type of nanofiber). In other embodiments, thelithium-containing-nanofibers comprise non-aggregatedlithium-containing-domains embedded within a continuous nanofiber matrixor backbone. In specific embodiments, the continuous nanofiber matrix orbackbone comprises or is carbon (e.g., amorphous or amorphous andcrystalline carbon). In some embodiments, provided herein are batteries(e.g., lithium-ion batteries) comprising an anode, an electrolyte and apositive electrode (cathode) comprising a plurality oflithium-containing-nanofibers.

In some embodiments, a nanofiber comprising a lithium material comprisesa lithium-containing-material resented by the formula: Li_(a)M_(b)X_(c).In some embodiments, M is Fe, Ni, Co, Mn, V, Al, Li, or a combinationthereof. In certain embodiments, X is O, PO₄, or SiO₄. In someembodiments, a is 1-2; b is 0-2; and c is 1-4. In specific embodiments,M is Ni, Co, Mn, or a combination thereof. In further or alternativespecific embodiments, X is O. In some specific embodiments, a is 1 and bis 1. In more specific embodiments, a is 1, b is 1, and c is 2. In otherspecific embodiments, a is 1 and b is 2. In more specific embodiments, ais 1, b is 2, and c is 4. In some embodiments, thelithium-containing-material is LiCoO₂, LiNiO₂,LiNi_(0.4)Co_(0.4)Mn_(0.2)O₂, LiNi_(1/3)Co_(1/3)O₂,LiMn_(1.5)Ni_(0.5)O₄, or LiFePO₄. In other embodiments, thelithium-containing material is Li₂SO_(y′), wherein y′ is 0-4. In morespecific embodiments, the lithium-containing material is Li₂S or Li₂SO₄.

In some embodiments, the nanofiber comprises a Li₂S/carbon nanocomposite(e.g., lithium sulfide domains in a continuous carbon matrix) or aLi₂SO₄/carbon nanocomposite (e.g., lithium sulfate in a continuouscarbon matrix).

In some embodiments, the lithium-containing-material comprises at least50 wt. % (e.g., at least 80 wt. %) of the nanofiber. In further oralternative embodiments, the nanofiber comprises at least 2.5 wt. %lithium. In further or alternative embodiments, at least 10% (e.g.,about 25%) of the atoms present in the nanofiber are lithium atoms.

In some embodiments, the nanofibers provided herein have an initialcapacity (e.g., specific, charge or discharge capacity) of at least 60mAh/g as a positive electrode (cathode) in a lithium ion battery (e.g.,at a charge/discharge rate of 0.1 C in a full or half-cell). In specificembodiments, the nanofibers provided herein have an initial capacity ofat least 75 mAh/g as a positive electrode (cathode) in a lithium ionbattery (e.g., at a charge/discharge rate of 0.1 C in a half-cell). Inmore specific embodiments, the nanofibers provided herein have aninitial capacity of at least 100 mAh/g as a positive electrode (cathode)in a lithium ion battery (e.g., at a charge/discharge rate of 0.1 C in ahalf-cell). In still more specific embodiments, the nanofibers providedherein have an initial capacity of at least 120 mAh/g as a positiveelectrode (cathode) in a lithium ion battery (e.g., at acharge/discharge rate of 0.1 C in a half-cell). In yet more specificembodiments, the nanofibers provided herein have an initial capacity ofat least 150 mAh/g as a positive electrode (cathode) in a lithium ionbattery (e.g., at a charge/discharge rate of 0.1 C in a half-cell). Inmore specific embodiments, the nanofibers provided herein have aninitial capacity of at least 175 mAh/g as a positive electrode (cathode)in a lithium ion battery (e.g., at a charge/discharge rate of 0.1 C in ahalf-cell).

In some embodiments, nanofibers provided herein have a capacity (e.g.,specific, charge or discharge) retention as a positive electrode(cathode) in a lithium ion battery (e.g., at a charge/discharge rate ofat least 0.1 C in a full or half-cell) of at least 50% after 50 cycles.In specific embodiments, nanofibers provided herein have a capacityretention as a positive electrode (cathode) in a lithium ion battery(e.g., at a charge/discharge rate of at least 0.1 C in a full orhalf-cell) of at least 60% after 50 cycles. In more specificembodiments, nanofibers provided herein have a capacity retention as apositive electrode (cathode) in a lithium ion battery (e.g., at acharge/discharge rate of at least 0.1 C in a full or half-cell) of atleast 70% after 50 cycles. FIG. 4 and FIG. 13 illustrate capacityretention for various nanofibers provided herein.

Also provided herein are as-spun hybrid nanofibers comprising polymerand a lithium component. In some embodiments, the nanofiber comprises acontinuous polymer matrix and a lithium component. In specificembodiments, the polymer matrix comprising a polymer comprising amonomeric repeat unit of (CH₂-CHOM¹), each M¹ being independentlyselected from H, a lithium ion, and a metal radical; at least 5% of M¹is L⁺. In some embodiments, the metal radical is a metal halide, a metalcarboxylate, a metal alkoxide, a metal diketone, a metal nitrate, or acombination thereof. In specific embodiments, at least 10% of M¹ is Li⁺.In further or alternative embodiments, at least 10% (e.g., at least 20%,at least 25%, or at least 40%) of M¹ is cobalt radical or ion (e.g.,—CoOCOCH₃). In further or alternative embodiments, at least 10% (e.g.,at least 20%, at least 25%, or at least 40%) of M¹ is manganese radicalor ion (e.g., —MnOCOCH₃). In further or alternative embodiments, atleast 10% (e.g., at least 20%, at least 25%, or at least 40%) of M¹ isnickel acetate (e.g., —NiOCOCH₃).

In some embodiments, a nanofiber provided herein has a diameter of lessthan 1 micron (e.g., less than 500 nm). In further or alternativeembodiments, a nanofiber provided herein has an aspect ratio of at least100 (e.g., at least 1,000, or at least 10,000). In further oralternative embodiments, a nanofiber provided herein has a specificsurface are of at least 10 m²/g (e.g., at least 30 m²/g, at least 100m²/g, at least 300 m²/g, at least 500 m²/g, or at least 1000 m²/g, e.g.,as measured by BET). In further or alternative embodiments, a nanofiberprovided herein has a length of at least 1 micron (e.g., at least 10microns, at least 100 microns, at least 1,000 microns).

In some embodiments, a nanofiber provided herein comprises a backbone ofa first material, the backbone comprising non-aggregated nanoparticlesembedded therein, the nanoparticles comprising alithium-containing-material. In specific embodiments, the backbonecomprises carbon. In specific embodiments, the lithium containingmaterial is represented by the formula: Li_(a)M_(b)X_(c), e.g., whereina, b, c, M and X are as discussed above.

In some embodiments, provided herein is a lithium-ion battery comprisingan anode in a first chamber, a cathode in a second chamber, and aseparator between the first chamber and the second chamber, the cathodecomprising a plurality of nanofibers of any one of the preceding claims.

In addition, provided herein are processes for producing alithium-containing-nanofiber, the processes comprising electrospinning afluid stock to produce a first (as-spun) nanofiber, the fluid stockcomprising or prepared by combining a polymer and a lithium salt. Inspecific embodiments, the first (as-spun) nanofiber is then thermallytreated to produce the lithium containing nanofiber. In someembodiments, the electrospinning of the fluid stock is gas assisted(e.g., coaxially—along or around the same axis). In specificembodiments, the polymer polyacrylonitrile (PAN) (e.g., wherein thefluid further comprises DMF), polyvinyl alcohol (PVA) (e.g., wherein thefluid further comprises water), or a combination thereof. In someembodiments, the fluid stock is aqueous. In certain embodiments, thefluid stock further comprises a non-lithium metal precursor. In specificembodiments, the metal precursor is an iron precursor, a cobaltprecursor, an aluminum precursor, a nickel precursor, a manganeseprecursor, or a combination thereof. In some embodiments, the processcomprises thermally treating the first nanofiber at a temperature of atleast 300° C. In certain embodiments, the combined concentration oflithium salt and metal precursor is present in or provided into thefluid stock in a concentration of at least 200 mM (e.g., at least 250mM, or at least 300 mM). In some embodiments, the polymer comprises aplurality of repeating monomeric residues, the combined lithium salt andmetal precursor being present in or added in a lithium salt/metalprecursor-to-monomeric residue ratio of at least 1:4 (e.g., at least1:2, or at least 1:1). In some embodiments, the thermally treating stepis performed under air—e.g., wherein the process produces a nanofibercomprising a continuous matrix of lithium metal oxide. In someembodiments, the fluid stock further comprises a calcination reagent,such as a non-metal precursor. In specific embodiments, the non-metalprecursor is elemental sulfur or a phosphite alkoxide. In someembodiments, the non-metal precursor is elemental sulfur—e.g., forproducing lithium containing nanofiber comprising lithium sulfide. Incertain embodiments, the non-metal precursor is a phosphitealkoxide—e.g., for producing lithium containing nanofiber comprisinglithium metal phosphate.

In certain embodiments, provided herein is a process for producing alithium-containing-nanofiber, the process comprising:

-   -   a. electrospinning (e.g., gas assisted electrospinning, such as        coaxially gas assisted) a fluid stock to produce a first        (as-spun) nanofiber, the fluid stock comprising polymer and a        plurality of nanoparticles, the nanoparticles comprising a        lithium-containing-material; and    -   b. thermally treating the first nanofiber to produce the lithium        containing nanofiber.

Also, provided in certain embodiments herein methods for producingpositive electrode, the methods comprising, for example:

-   -   a. electrospinning a fluid stock to form nanofibers, the fluid        stock comprising a lithium material and a polymer (e.g., a        polymer electrospinnable as a melt or in solution—aqueous or        solvent based);    -   b. thermally treating the nanofibers; and    -   c. assembling the nanofibers into an electrode.

Lithium-containing nanofibers described herein are optionally preparedby the first step alone or by the first and second steps.

Further embodiments are also contemplated herein, such as thosedescribed in the claims and the detailed description. Moreover,disclosure of a single nanofiber having a given characteristic orcharacteristics includes disclosure of a plurality of nanofibers havingan average of the given characteristic or characteristics. Similarly,disclosure of an average characteristic for a plurality of fibersincludes disclosure of a specific characteristic for a single fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 illustrates one embodiment of the method for producinglithium-containing nanofibers described herein (e.g., suitable for usein lithium ion batteries).

FIG. 2 shows a TEM image of LiCoO₂ nanofibers from electrospinning ofaqueous solution of PVA/Li-Ac/Co—Ac followed by thermal treatment at800° C. under air.

FIG. 3 shows an XRD spectra of LiCoO₂ nanofibers from electrospinning ofaqueous solution of PVA/Li—Ac/Co—Ac followed by thermal treatment at800° C. under air, confirming the formation of nanocrystals LiCoO₂.

FIG. 4 illustrates the charge/discharge capacities for lithium cobaltoxide prepared using a one step thermal process (panel A) and a two stepthermal process (panel B).

FIG. 5 illustrates (panel B) an SEM image of certainLi(Ni_(1/3)Co_(1/3)Mn_(1/3))O₂ nanofibers (i.e., nanofibers comprising acontinuous core matrix, or backbone, of Li(Ni_(1/3)Co_(1/3)Mn_(1/3))O₂),as well as as-spun precursor nanofibers used to prepare the same (panelA).

FIG. 6 illustrates an XRD pattern for certainLi(Ni_(1/3)Co_(1/3)Mn_(1/3))O₂ nanofibers.

FIG. 7 illustrates charge/discharge capacities for certainLi(Ni_(1/3)Co_(1/3)Mn_(1/3))O₂ nanofibers in a lithium ion battery halfcell.

FIG. 8 illustrates (panel B) an SEM image of certainLi[Li_(0.2)Mn_(0.56)Ni_(0.16) Co_(0.08)]O₂ nanofibers (i.e., nanofiberscomprising a continuous core matrix, or backbone, ofLi[Li_(0.2)Mn_(0.56)Ni_(0.16)Co_(0.08)]O₂), as well as as-spun precursornanofibers used to prepare the same (panel A).

FIG. 9 illustrates charge/discharge capacities for certainLi[Li_(0.2)Mn_(0.56)Ni_(0.16)Co_(0.08)]O₂ nanofibers.

FIG. 10 illustrates (panel B) an SEM image of certainLi_(0.8)Mn_(0.4)Ni_(0.4) Co_(0.4)O₂ nanofibers (i.e., nanofiberscomprising a continuous core matrix, or backbone, ofLi_(0.8)Mn_(0.4)Ni_(0.4)Co_(0.4)O₂), as well as as-spun precursormonofibers used to prepare the same (panel A).

FIG. 11 illustrates (panel B) an SEM image of certain LiMn₂O₄ nanofibers(i.e., nanofibers comprising a continuous core matrix, or backbone, ofLiMn₂O₄), as well as as-spun precursor nanofibers used to prepare thesame (panel A). Panel C illustrates a TEM image of certain LiMn₂O₄nanofibers.

FIG. 12 illustrates an XRD pattern for certain LiMn₂O₄ nanofibers.

FIG. 13 illustrates charge/discharge capacity for certain LiMn₂O₄nanofibers in a lithium ion battery half cell.

FIG. 14 illustrates an XRD pattern for certain LiMn₂O₄ nanofibers dopedwith nickel Li(Ni_(x)Mn_(z))O₄.

FIG. 15 illustrates (panel B) an SEM image of certain lithium ironphosphate nanofibers (i.e., nanofibers comprising a continuous corematrix, or backbone, of lithium iron phosphate), as well as as-spunprecursor nanofibers used to prepare the same (panel A).

FIG. 16 illustrates an XRD pattern for certain lithium iron phosphatenanofibers.

FIG. 17 illustrates an SEM image of certain Li₂S/C nanofibers, as wellas as-spun precursor nanofibers used to prepare the same (panel A).

FIG. 18 illustrates an XRD pattern for certain Li₂SO₄/C nanofibers.

FIG. 19 illustrates a co-axial electrospinning needle apparatus that maybe used for gas assisted electrospinning of a single fluid or formultilayered coaxial electrospinning (multi-layered gas assistedelectrospinning is possible with an additional needle in the needleapparatus configured around the illustrated needles and aligned alongthe common axis).

DETAILED DESCRIPTION OF THE INVENTION

Provided herein are lithium containing nanofibers and nanofiber mats andprocesses for preparing silicon containing nanofibers and nanofibermats. Also provided herein are lithium ion batteries comprising suchnanofibers (e.g., as the positive electrode or cathode). In someembodiments, a nanofiber (e.g., of a plurality of nanofibers, of ananofiber mat, or of a process described herein) comprise a lithiummaterial (e.g., a continuous matrix of a lithium material). In certainembodiments, a nanofiber provided herein comprises a first material anda second material, the first material comprising a lithium material. Infurther embodiments, the first material, the second material, or bothform a continuous matrix within the nanofiber. In specific embodiments,both the first and second materials form continuous matrix materialswithin the nanofiber. In other specific embodiments, the first materialcomprises a plurality of discrete domains within the nanofiber. In morespecific embodiments, the second material is a continuous matrixmaterial within the nanofiber.

Described in certain embodiments herein are batteries (e.g., lithium-ionbatteries) comprising an electrode and methods for making a battery(e.g., lithium ion battery) comprising an electrode. In someembodiments, the electrode comprises a plurality of nanofibers, thenanofibers comprising domains of a high energy capacity material. Insome embodiments, the electrode comprises porous nanofibers, thenanofibers comprising a high energy capacity material.

Described in certain embodiments herein are batteries (e.g., lithium-ionbatteries) and methods for making a battery (e.g., lithium ion battery)comprising a separator. In some embodiments, the battery comprises ananode in a first chamber, a cathode in a second chamber, and a separatorbetween the first chamber and the second chamber. In some embodiments,the separator comprises polymer nanofibers. In some embodiments, theseparator allows ion transfer between the first chamber and secondchamber in a temperature dependent manner.

In some embodiments, the lithium-ion battery comprises an electrolyte.

Lithium Materials

In some embodiments, the lithium material is any material capable ofintercalating and deintercalating lithium ions. In some embodiments, thelithium material is or comprises a lithium metal oxide, a lithium metalphosphate, a lithium metal silicate, a lithium metal sulfate, a lithiummetal borate, or a combination thereof. In specific embodiments, thelithium material is a lithium metal oxide. In other specificembodiments, the lithium material is a lithium metal phosphate. In otherspecific embodiments, the lithium material is a lithium metal silicate.In other specific embodiments, the lithium material is lithium sulfide.

In some embodiments, provided herein is a nanofiber comprising a lithiummaterial (e.g., a continuous core matrix of a lithium material). In someembodiments, the nanofibers comprise a continuous matrix of a lithiummaterial. In certain embodiments, the nanofibers comprises a continuousmatrix material (e.g., carbon, ceramic, or the like) and discretedomains of a lithium material (e.g., wherein the discrete domains arenon-aggregated). In specific embodiments, the continuous matrix materialis a conductive material (e.g., carbon). In further embodiments,provided herein is a cathode (or positive electrode) comprising aplurality of nanofibers comprising a lithium material. In someembodiments, less than 40% of the nanoparticles are aggregated (e.g., asmeasured in any suitable manner, such as by TEM). In specificembodiments, less than 30% of the nanoparticles are aggregated). In morespecific embodiments, less than 25% of the nanoparticles areaggregated). In yet more specific embodiments, less than 20% of thenanoparticles are aggregated). In still more specific embodiments, lessthan 10% of the nanoparticles are aggregated). In more specificembodiments, less than 5% of the nanoparticles are aggregated).

In some instances, the lithium material is or comprises LiCoO₂,LiCo_(x1)Ni_(y1)Mn_(z1)O₂, LiMn_(x1)Ni_(y1)Co_(z1)V_(a1)O₄, Li₂S,LiFe_(x1)Ni_(y1)Co_(z1)V_(a1)PO₄, any oxidation state thereof, or anycombination thereof. Generally, x1, y1, z1, and a1 are independentlyselected from suitable numbers, such as a number from 0 to 5 or fromgreater than 0 to 5.

In certain embodiments, provided herein is a plurality of nanofibers,the nanofibers comprising lithium, such as a continuous matrix of alithium containing material (e.g., a lithium salt or lithiumalloy/insertion compound, such as a lithium metal oxide). In otherembodiments, provided herein is an electrode (e.g., positive electrodeor cathode) comprising a plurality of nanofibers, the nanofiberscomprising (a) a continuous matrix material; and (b) discrete, isolateddomains comprising lithium. In some embodiments, the continuous matrixor isolated domains comprise lithium in the form of a lithium containingmetal alloy. In specific embodiments, the lithium containing metal alloyis a lithium metal oxide. In some embodiments, the nanofiber(s) comprisea lithium containing material of the following formula (I):

Li_(a)M_(b)X_(c)   (I)

In certain embodiments, M represents one or more metal element (e.g., Mrepresents Fe, Ni, Co, Mn, V, Ti, Zr, Ru, Re, Pt, Bi, Pb, Cu, Al, Li, ora combination thereof) and X represents one or more non-metal (e.g., Xrepresents C, N, O, P, S, SO₄, PO₄, Se, halide, F, CF, SO₂, SO₂ Cl₂, I,Br, SiO₄, BO₃, or a combination thereof) (e.g., a non-metal anion). Insome embodiments, a is 0.5-5, or 1-5 (e.g., 1-2), b is 0-2, and c is0-10 (e.g., 1-4, or 1-3).

In some embodiments, X is selected from the group consisting of O, SO₄,PO₄, SiO₄, BO₃. In more specific embodiments, X is selected from thegroup consisting of O, PO₄, and SiO₄. In certain embodiments, M is Mn,Ni, Co, Fe, V, Al, or a combination thereof.

In certain embodiments, a lithium material of formula (I) is LiMn₂O₄,LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂, LiCoO₂, LiNiO₂, LiFePO₄, Li₂FePO₄F, or thelike. In some embodiments, a lithium material of formula (I) isLiNi_(b1)Co_(b2)Mn_(b3)O₂, wherein b1+b2+b3=1, and wherein 0<b1, b2,b3<1. In some embodiments, a lithium material of formula (I) isLiNi_(b1)Co_(b2)Al_(b3)O₂, wherein b1+b2+b3=1, and wherein 0<b1, b2,b3<1. In certain embodiments, a lithium material of formula (I) isLiMn₂O₄, LiMn_(b1)Fe_(b2)O₄ (wherein b1+b2=2, e.g., b1=1.5), LiMnPO₄,LiNiPO₄, LiCoPO₄, Li₃V₂(PO₄)₃, Li₂FeSiO₄, Li₂MnSiO₄, LiFeBO₃, orLiMnBO₃.

In some embodiments, the lithium material of formula (I) is Li₂SO_(y′),wherein y′ is 0-4, such as Li₂S or Li₂SO₄.

In more specific embodiments, the lithium metal of formula (I) isrepresented by the lithium metal of formula (Ia):

Li_(a)M_(b)O₂   (Ia)

In specific embodiments, M, a, and b are as described above. In specificembodiments, a lithium metal of formula (Ia) has the structure LiMO₂(e.g., LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂). In some embodiments, a and b areeach 1 and the one or more metal of M have an average oxidation state of3.

In more specific embodiments, the lithium metal of formula (Ia) isrepresented by the lithium metal of formula (Ib):

Li(M′_((1-g))Mn_(g))O₂   (Ib)

In certain embodiments, M′ represents one or more metal element (e.g.,M′ represents Fe, Ni, Co, Mn, V, Li, Cu, Zn, or a combination thereof).In some embodiments, g is 0-1 (e.g., 0<g<1). In specific embodiments, M′represents one or more metal having an average oxidation state of 3.

In more specific embodiments, the lithium metal of formula (Ia) or (Ib)is represented by the lithium metal of formula (Ic):

Li[Li_((1-2h)/3))M″_(h)Mn_((2-h)/3))O₂   (Ic)

In certain embodiments, M″ represents one or more metal element (e.g.,M″ represents Fe, Ni, Co, Zn, V, or a combination thereof). In someembodiments, h is 0-0.5 (e.g., 0<h<0.5, such as 0.083<h<0.5). In aspecific embodiment, the lithium metal of formula (Ic) isLi[Li_((1-2h)/3)Ni_(h′)Co_((h-h′))Mn_((2-h)/3))O₂, wherein h′ is 0-0.5(e.g., 0<h′<0.5).

In more specific embodiments, the lithium metal of formula (Ia) isrepresented by the lithium metal of formula (Id):

LiNi_(b′)Co_(b″)M′″_(b″′)O₂   (Id)

In certain embodiments, M″′ represents one or more metal element (e.g.,M″′ represents Fe, Mn, Zn, V, or a combination thereof). In someembodiments, each of b′, b″, and b″′ is independently 0-2 (e.g., 0-1,such as 0<b′, b″, and b″′<1). In specific embodiments, the sum of b′,b″, and b″′ is 1. In some embodiments, the one or more metal of M″′ whentaken together with the Ni and Co have an average oxidation state of 3.

In some embodiments, the lithium metal of formula (I) is represented bythe lithium metal of formula (Ie):

Li_(a)M_(b)O₃   (Ie)

In specific embodiments, M, a, and b are as described above. In specificembodiments, a lithium metal of formula (Ie) has the structure Li₂MO₃(e.g., Li₂MnO₃). In some embodiments, a is 2, b is 1 and the one or moremetal of M have an average oxidation state of 4.

In certain embodiments, provided herein is an electrode (e.g., positiveelectrode or cathode) comprising a plurality of nanofibers, thenanofibers comprising a continuous matrix of a lithium containing metal(e.g., a lithium metal alloy, such as a lithium metal oxide). In otherembodiments, provided herein is an electrode (e.g., positive electrodeor cathode) comprising a plurality of nanofibers, the nanofiberscomprising (a) a continuous matrix material; and (b) discrete, isolateddomains of a lithium containing metal (e.g., a lithium metal alloy, suchas a lithium metal oxide).

In some embodiments, the plurality of nanofibers have a continuousmatrix of a lithium containing material. In certain embodiments, thecontinuous matrix of lithium containing material is porous (e.g.,mesoporous). In certain embodiments, the continuous matrix of lithiumcontaining material is hollow (e.g., hollow lithium containing metalnanofibers).

In specific embodiments, the nanofibers comprise (e.g., on average) atleast 50% lithium containing material (e.g., by elemental analysis). Inspecific embodiments, the nanofibers comprise (e.g., on average) atleast 70% lithium containing material. In more specific embodiments, thenanofibers comprise (e.g., on average) at least 80% lithium containingmaterial. In still more specific embodiments, the nanofibers comprise(e.g., on average) at least 90% lithium containing material. In yet morespecific embodiments, the nanofibers comprise e.g., on average) at least95% lithium containing material.

In certain embodiments, the nanofibers comprise (e.g., on average) atleast 0.5 wt. % lithium (e.g., by elemental analysis). In specificembodiments, the nanofibers comprise (e.g., on average) at least 1 wt. %lithium (e.g., by elemental analysis). In more specific embodiments, thenanofibers comprise (e.g., on average) at least 1.5 wt. % lithium (e.g.,by elemental analysis). In still more specific embodiments, thenanofibers comprise (e.g., on average) at least 5 wt. % lithium (e.g.,by elemental analysis). In specific embodiments, the nanofibers comprise(e.g., on average) at least 7 wt. % lithium (e.g., by elementalanalysis). In more embodiments, the nanofibers comprise (e.g., onaverage) at least 10 wt. % lithium (e.g., by elemental analysis).

In some embodiments, lithium atoms constitute (e.g., on average) atleast 10% of the atoms present in the nanofibers. In specificembodiments, lithium atoms constitute (e.g., on average) at least 20% ofthe atoms present in the nanofibers. In more specific embodiments,lithium atoms constitute (e.g., on average) at least 30% of the atomspresent in the nanofibers. In still more specific embodiments, lithiumatoms constitute (e.g., on average) at least 40% of the atoms present inthe nanofibers. In yet more specific embodiments, lithium atomsconstitute (e.g., on average) at least 50% of the atoms present in thenanofibers. For example, in certain embodiments, provided herein arenanofibers comprising pure LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂, which comprisesabout 7 wt. % lithium (6.94 mol wt. Li/96.46 mol wt.LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂) and about 25% lithium atoms (1 lithiumatom/(1 lithium atom+⅓ nickel atom+⅓ manganese atom+⅓ cobalt atom+2oxygen atoms)).

In some embodiments, the electrode comprises a plurality of nanofiberscomprising (a) a matrix; and (b) a plurality of isolated, discretedomains comprising a lithium containing metal (e.g., a lithiumalloy/intercalculation compound, such as a lithium metal oxide). Inspecific embodiments, the matrix is a continuous matrix of carbon (e.g.,amorphous carbon). In certain embodiments, the matrix and/or discretelithium containing domains are porous (e.g., mesoporous). In certainembodiments, the continuous matrix is hollow. In specific embodiments,the nanofibers comprise (e.g., on average) at least 30% lithium material(e.g., by elemental analysis). In specific embodiments, the nanofiberscomprise (e.g., on average) at least 40% lithium material. In morespecific embodiments, the nanofibers comprise (e.g., on average) atleast 50% lithium material. In still more specific embodiments, thenanofibers comprise (e.g., on average) at least 70% lithium material. Inyet more specific embodiments, the nanofibers comprise (e.g., onaverage) at least 80% lithium material. In some embodiments, thenanofibers comprise lithium containing domains that comprise (e.g., onaverage) at least 70% lithium material. In more specific embodiments,the domains comprise (e.g., on average) at least 80% lithium material.In still more specific embodiments, the domains comprise (e.g., onaverage) at least 90% lithium material. In yet more specificembodiments, the domains comprise (e.g., on average) at least 95%lithium material. In certain embodiments, the nanofibers comprise (e.g.,on average) at least 0.1 wt. % lithium (e.g., by elemental analysis). Inspecific embodiments, the nanofibers comprise (e.g., on average) atleast 0.5 wt. % lithium (e.g., by elemental analysis). In more specificembodiments, the nanofibers comprise (e.g., on average) at least 1 wt. %lithium (e.g., by elemental analysis). In still more specificembodiments, the nanofibers comprise (e.g., on average) at least 2.5 wt.% lithium (e.g., by elemental analysis). In specific embodiments, thenanofibers comprise (e.g., on average) at least 5 wt. % lithium (e.g.,by elemental analysis). In more embodiments, the nanofibers comprise(e.g., on average) at least 10 wt. % lithium (e.g., by elementalanalysis). In some embodiments, lithium atoms constitute (e.g., onaverage) at least 10% of the atoms present in the nanofibers. Inspecific embodiments, lithium atoms constitute (e.g., on average) atleast 5% of the atoms present in the nanofibers or the domains. In morespecific embodiments, lithium atoms constitute (e.g., on average) atleast 10% of the atoms present in the nanofibers or domains. In stillmore specific embodiments, lithium atoms constitute (e.g., on average)at least 20% of the atoms present in the nanofibers or domains. In yetmore specific embodiments, lithium atoms constitute (e.g., on average)at least 30% of the atoms present in the nanofibers or domains. Infurther embodiments, lithium atoms constitute (e.g., on average) atleast 40%, at least 50%, or the like of the atoms present in thedomains.

In certain embodiments, provided herein arelithium-containing-nanofibers comprising a lithium material describedherein, wherein up to 50% of the lithium is absent. In some instances,the lithium is absent due to delithiation (de-intercalculation oflithium) during lithium ion battery operation. In other instances, thelithium is absent due to volatility and/or sublimation of the lithiumcomponent. In specific embodiments, up to 40% of the lithium is absent.In more specific embodiments, up to 30% of the lithium is absent. Instill more specific embodiments, up to 20% of the lithium is absent. Inyet more specific embodiments, up to 10% of the lithium is absent.

In some embodiments, provided herein is a battery comprising such anelectrode (e.g., cathode). In specific embodiments, the battery is asecondary cell. Also, provided in certain embodiments herein arenanofibers or nanofiber mats comprising one or more such nanofiber asdescribed herein.

In some embodiments, positive electrodes provided herein are prepared bydepositing lithium-containing nanofibers onto a current collector (e.g.,copper or aluminum), thereby creating a positive electrode comprisingthe nanofibers in contact with a current collector. In certainembodiments, as-treated nanofibers are ground in a mortal and pestle toproduce processed nanofibers, which are then deposited on a currentcollector. In some embodiments, the processed nanofibers are dispersedin a solvent to prepare a composition, the composition is deposited ontoa current collector, and evaporation of the solvent results in formationof an electrode on the current collector. In specific embodiments, thecomposition further comprises a binder. In further or alternativespecific embodiments, the composition further comprises a conductivematerial (e.g., carbon black)—e.g., to improve electron mobility.

Nanofibers

In some embodiments, the nanofibers provide herein comprise a backbonematerial (a core matrix material). In specific embodiments, the backbonematerial is a lithium material described herein. In other specificembodiments, the backbone material is a continuous matrix material withnon-aggregated domains embedded therein, the non-aggregated domainscomprising a lithium material described herein (e.g., a nanoparticlecomprising a lithium material described herein). In certain embodiments,nanofibers described herein comprise a hollow core. In specificembodiments, the nanofibers described herein comprise a continuousmatrix material surrounding the hollow core. In more specificembodiments, the continuous matrix material comprises a lithium materialdescribed herein. In other specific embodiments, the continuous matrixmaterial comprises non-aggregated domains embedded therein, thenon-aggregated domains comprising a lithium material described herein(e.g., a nanoparticle comprising a lithium material described herein).In various embodiments herein, a continuous matrix material is comprisesa ceramic, a metal, or carbon. In specific embodiments, the continuousmatrix material is a conductive material.

The nanofibers have any suitable diameter. In some embodiments, acollection of nanofibers comprises nanofibers that have a distributionof fibers of various diameters. In some embodiments, a single nanofiberhas a diameter that varies along its length. In some embodiments, fibersof a population of nanofibers or portions of a fiber accordingly exceedor fall short of the average diameter. In some embodiments, thenanofiber has on average a diameter of about 20 nm, about 30 nm, about40 nm, about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 90 nm,about 100 nm, about 130 nm, about 150 nm, about 200 nm, about 250 nm,about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm,about 800 nm, about 900 nm, about 1,000 nm, about 1,500 nm, about 2,000nm and the like. In some embodiments, the nanofiber has on average adiameter of at most 20 nm, at most 30 nm, at most 40 nm, at most 50 nm,at most 60 nm, at most 70 nm, at most 80 nm, at most 90 nm, at most 100nm, at most 130 nm, at most 150 nm, at most 200 nm, at most 250 nm, atmost 300 nm, at most 400 nm, at most 500 nm, at most 600 nm, at most 700nm, at most 800 nm, at most 900 nm, at most 1,000 nm, at most 1,500 nm,at most 2,000 nm and the like. In some embodiments, the nanofiber has onaverage a diameter of at least 20 nm, at least 30 nm, at least 40 nm, atleast 50 nm, at least 60 nm, at least 70 nm, at least 80 nm, at least 90nm, at least 100 nm, at least 130 nm, at least 150 nm, at least 200 nm,at least 250 nm, at least 300 nm, at least 400 nm, at least 500 nm, atleast 600 nm, at least 700 nm, at least 800 nm, at least 900 nm, atleast 1,000 nm, at least 1,500 nm, at least 2,000 nm and the like. Inyet other embodiments, the nanofiber has on average a diameter betweenabout 50 nm and about 300 nm, between about 50 nm and about 150 nm,between about 100 nm and about 400 nm, between about 100 nm and about200 nm, between about 500 nm and about 800 nm, between about 60 nm andabout 900 nm, and the like.

“Aspect ratio” is the length of a nanofiber divided by its diameter. Insome embodiments, aspect ratio refers to a single nanofiber. In someembodiments, aspect ratio is applied to a plurality of nanofibers andreported as a single average value, the aspect ratio being the averagelength of the nanofibers of a sample divided by their average diameter.Diameters and/or lengths are measured by microscopy in some instances.The nanofibers have any suitable aspect ratio. In some embodiments thenanofiber has an aspect ratio of about 10, about 10², about 10³, about10⁴, about 10⁵, about 10⁶, about 10⁷, about 10⁸, about 10⁹, about 10¹⁰,about 10¹¹, about 10¹², and the like. In certain embodiments thenanofiber has an aspect ratio of at least 10, at least 10², at least10³, at least 10⁴, at least 10⁵, at least 10⁶, at least 10⁷, at least10⁸, at least 10⁹, at least 10¹⁰, at least 10¹¹, at least 10¹², and thelike. In other embodiments, the nanofiber is of substantially infinitelength and has an aspect ratio of substantially infinity.

In certain embodiments, the lithium material (e.g., core matrix lithiummaterial) provided herein is crystalline. In some embodiments, thelithium material comprises a layered crystalline structure. In certainembodiments, the lithium material comprises a spinel crystallinestructure. In certain embodiments, the lithium material comprises anolivine crystalline structure.

In some embodiments, domains of lithium material provided herein haveany suitable size. In some instances, the domains have an averagediameter of about 5 nm, about 10 nm, about 20 nm, about 30 nm, about 40nm, about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 90 nm,about 100 nm, about 130 nm, about 150 nm, about 200 nm, and the like. Insome instances, the domains have an average diameter of at most 5 nm, atmost 10 nm, at most 20 nm, at most 30 nm, at most 40 nm, at most 50 nm,at most 60 nm, at most 70 nm, at most 80 nm, at most 90 nm, at most 100nm, at most 130 nm, at most 150 nm, at most 200 nm, and the like.

In one aspect, the domains of high energy material have a uniform size.In some instances, the standard deviation of the size of the domains isabout 50%, about 60%, about 70%, about 80%, about 100%, about 120%,about 140%, about 200%, and the like of the average size of the domains(i.e., the size is uniform). In some instances, the standard deviationof the size of the domains is at most 50%, at most 60%, at most 70%, atmost 80%, at most 100%, at most 120%, at most 140%, at most 200%, andthe like of the average size of the domains (i.e., the size is uniform).

The domains of high energy material have any suitable distance betweeneach other (separation distance). In some instances, the domains have anaverage separation distance of about 2 nm, about 5 nm, about 10 nm,about 20 nm, about 30 nm, about 40 nm, about 50 nm, about 60 nm, about70 nm, about 80 nm, about 90 nm, about 100 nm, about 130 nm, about 150nm, about 200 nm, and the like. In some instances, the domains have anaverage diameter of at most 2 nm, at most 5 nm, at most 10 nm, at most20 nm, at most 30 nm, at most 40 nm, at most 50 nm, at most 60 nm, atmost 70 nm, at most 80 nm, at most 90 nm, at most 100 nm, at most 130nm, at most 150 nm, at most 200 nm, and the like.

In some embodiments, the domains are uniformly distributed within thenanofiber matrix. In some instances, the standard deviation of thedistances between a given domain and the nearest domain to the givendomain is about 50%, about 60%, about 70%, about 80%, about 100%, about120%, about 140%, about 200%, and the like of the average of thedistances (i.e., uniform distribution). In some instances, the standarddeviation of the distances between a given domain and the nearest domainto the given domain is at most 50%, at most 60%, at most 70%, at most80%, at most 100%, at most 120%, at most 140%, at most 200%, and thelike of the average of the distances (i.e., uniform distribution). Insome embodiments, less than 40% of the domains (e.g., nanoparticles) areaggregated (e.g., as measured in any suitable manner, such as by TEM).In specific embodiments, less than 30% of the domains are aggregated. Inmore specific embodiments, less than 25% of the domains are aggregated.In yet more specific embodiments, less than 20% of the domains areaggregated. In still more specific embodiments, less than 10% of thedomains are aggregated. In more specific embodiments, less than 5% ofthe domains are aggregated.

The domains of lithium material comprise any suitable mass of thenanofiber. In some instances, the domains comprise about 10%, about 20%,about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about90%, and the like of the mass of the nanofiber. In some instances, thedomains comprise at least 10%, at least 20%, at least 30%, at least 40%,at least 50%, at least 60%, at least 70%, at least 80%, at least 90%,and the like of the mass of the nanofiber. In some instances, thedomains comprise at most 10%, at most 20%, at most 30%, at most 40%, atmost 50%, at most 60%, at most 70%, at most 80%, at most 90%, and thelike of the mass of the nanofiber.

In various embodiments, the nanofibers have a high surface area andmethods are described for making nanofibers having a high surface area.In some embodiments, ordering of the pores results in a high surfacearea and/or specific surface area (e.g., surface area per mass ofnanofiber and/or surface area per volume of nanofiber) in someinstances. In certain embodiments, the nanofibers (e.g., porousnanofibers) provided herein have a specific surface area of at least 10m²/g, at least 50 m²/g, at least 100 m²/g, at least 200 m²/g, at least500 m²/g, at least 1,000 m²/g, at least 2,000 m²/g, at least 5,000 m²/g,at least 10,000 m²/g, and the like. The “specific surface area” is thesurface area of at least one fiber divided by the mass of the at leastone fiber. The specific surface area is calculated based on a singlenanofiber, or based on a collection of nanofibers and reported as asingle average value. Techniques for measuring mass are known to thoseskilled in the art. In some embodiments, the surface area is measured byphysical or chemical methods, for example by the Brunauer-Emmett, andTeller (BET) method where the difference between physisorption anddesorption of inert gas is utilized to determine the surface area or bytitrating certain chemical groups on the nanofiber to estimate thenumber of groups on the surface, which is related to the surface area bya previously determined titration curve. Those skilled in the art ofchemistry will be familiar with methods of titration.

The nanofiber has any suitable length. A given collection of nanofiberscomprises nanofibers that have a distribution of fibers of variouslengths. Therefore, certain fibers of a population accordingly exceed orfall short of the average length. In some embodiments, the nanofiber hasan (average) length of at least about 1 μm, at least about 10 μm, atleast about 20 μm, at least about 50 μm, at least about 100 μm, at leastabout 500 μm, at least about 1,000 μm, at least about 5,000 μm, at leastabout 10,000 μm, at least about 50,000 μm, at least about 100,000 μm, atleast about 500,000 μm, and the like. Methods for measuring the lengthof a nanofiber include, but are not limited to microscopy, optionallytransmission electron microscopy (“TEM”) or scanning electron microscopy(“SEM”).

In one aspect, the nanofiber has is substantially contiguous or has acontinuous matrix material. A nanofiber is substantially contiguous or amaterial constitutes a continuous matrix of the nanofiber if whenfollowing along the length of the nanofiber, the fiber material is incontact with at least some neighboring fiber material over substantiallythe entire nanofiber length. “Substantially” the entire length meansthat at least 80%, at least 90%, at least 95%, or at least 99% of thelength of the nanofiber is contiguous. The nanofiber is optionallysubstantially contiguous in combination with any of the porositiesdescribed herein (e.g., 35%).

In one aspect, the nanofiber is substantially flexible or non-brittle.Flexible nanofibers are able to deform when a stress is applied andoptionally return to their original shape when the applied stress isremoved. A substantially flexible nanofiber is able to deform by atleast 5%, at least 10%, at least 20%, at least 50%, and the like invarious embodiments. A non-brittle nanofiber does not break when astress is applied. In some embodiments, the nanofiber bends (e.g., issubstantially flexible) rather than breaks. A substantially non-brittlenanofiber is able to deform by at least 5%, at least 10%, at least 20%,at least 50%, and the like without breaking in various embodiments.

Process

In one aspect, a process is described for producing lithium containingnanofibers. In some embodiments the method comprises: (a)electrospinning a fluid stock to form nanofibers, the fluid stockcomprising (i) a lithium precursor or lithium containing nanoparticlesand (ii) a polymer; and (b) thermally treating the nanofibers. In someembodiments, electrospinning of the fluid stock is gas assisted (e.g.,coaxially gas assisted). In further embodiments, a lithium ion batteryelectrode is optionally formed using such nanofibers (or smallernanofibers, such as fragments produced by sonication of the thermallytreated nanofibers).

In specific embodiments, a process for producing lithium containingnanofibers comprises (a) electrospinning a fluid stock to form as-spunnanofibers, the fluid stock comprising lithium precursor, a second metalprecursor, and a polymer; and (b) thermally treating the as-spunnanofibers to produce the lithium containing nanofibers. In morespecific embodiments, the process further comprises chemically treating(e.g., oxidizing, such as with air) the nanofibers. In certainembodiments, the chemical treatment occurs simultaneously with step (b).In other embodiments, the chemical treatment step occurs after step (b).In certain embodiments, the electrospinning is gas assisted. In specificembodiments, the electrospinning is coaxially gas assisted. In someembodiments, the fluid stock is aqueous. In specific embodiments, thepolymer is a water soluble polymer, such as polyvinyl alcohol (PVA).

In specific embodiments, a process for producing lithium containingnanofibers comprises (a) electrospinning a fluid stock to form as-spunnanofibers, the fluid stock comprising a nanoparticle comprising alithium material and a polymer; and (b) thermally treating the as-spunnanofibers to produce the lithium containing nanofibers. In certainembodiments, the thermal treatment occurs under inert conditions (e.g.,in an argon atmosphere). In certain embodiments, the electrospinning isgas assisted. In specific embodiments, the electrospinning is coaxiallygas assisted. In some embodiments, the fluid stock is aqueous. Inspecific embodiments, the polymer is a water soluble polymer, such aspolyvinyl alcohol (PVA). In other embodiments, fluid is a solvent basedsolution. In some embodiments, the polymer is a solvent soluble polymer,such as polyacrylonitrile (PAN).

In some embodiments, gas assisted electrospinning processes or apparatusdescribed herein providing or providing a device configured to provide aflow of gas along the same axis as an electrospun fluid stock. In someinstances, that gas (or gas needle) is provided along the same axis withthe fluid stock (or fluid stock needle) (e.g., and adjacent thereto). Inspecific instances, the gas (or gas needle) is provided coaxially withthe fluid stock (or fluid stock needle). FIG. 19 illustrates co-axialelectrospinning apparatus 300. The coaxial needle apparatus comprises aninner needle 301 and an outer needle 302, both of which needles arecoaxially aligned around a similar axis 303 (e.g., aligned with 5degrees, 3 degrees, 1 degree, or the like). In some embodiments, furthercoaxial needles may be optionally placed around, inside, or between theneedles 301 and 302, which are aligned around the axis 303 (e.g., asillustrated in FIG. 1). In some instances, the termination of theneedles is optionally offset 304. In some embodiments, gas assistedelectrospinning is utilized (e.g., about a common axis with the jetelectrospun from a fluid stock described herein). Exemplary methods ofgas-assisted electrospinning are described in PCT Patent ApplicationPCT/US2011/024894 (“Electrospinning apparatus and nanofibers producedtherefrom”), which is incorporated herein for such disclosure. Ingas-assisted embodiments, the gas is optionally air or any othersuitable gas (such as an inert gas, oxidizing gas, or reducing gas). Insome embodiments, gas assistance increases the throughput of the processand/or reduces the diameter of the nanofibers. In some instances, gasassisted electrospinning accelerates and elongates the jet of fluidstock emanating from the electrospinner. In some instances, gas assistedelectrospinning facilitates uniform dispersion of nanoparticles in thenanofibers. For example, in some instances, gas assisted electrospinning(e.g., coaxial electrospinning of a gas—along a substantially commonaxis—with a fluid stock comprising lithium containing nanoparticles)facilitates dispersion or non-aggregation of the nanoparticles in theelectrospun jet and the resulting as-spun nanofiber (and subsequentnanofibers produced therefrom). In some embodiments, incorporating a gasstream inside a fluid stock produces hollow nanofibers.

Fluid Stocks

In some embodiments, the fluid stock comprises (i) a lithium-containingmaterial (e.g., as a nanoparticle) or (ii) a lithium precursor (e.g.,lithium salt). In specific embodiments, the fluid stock comprises alithium precursor and at least one additional metal precursor (e.g., acobalt precursor, a manganese precursor, a nickel precursor, or acombination thereof). In some embodiments, each metal precursor isindependently a metal acetate, metal nitrate, metal acetylacetonate,metal chloride, metal hydride, hydrates thereof, or any combinationthereof.

In some embodiments, the amount of lithium precursor and metal precursorutilized herein are used in a fluid stock or process described herein ina molar ratio that is the same as the lithium material being prepared.For example, in some embodiments wherein a nanofiber comprising acontinuous matrix of a lithium material of formula (I) is beingprepared, the lithium precursor to additional metal precursor is presentin an a:b ratio.

Li_(a)M_(b)X_(c)   (I)

In certain embodiments, excess lithium precursor is optionally utilized(e.g., to make up for lithium that may be lost to sublimation duringthermal processing). In some embodiments, at least a 50% molar excess oflithium is utilized. In other embodiments, at least a 100% molar excessis utilized. For example, the lithium precursor to additional metalprecursor for preparing a material of formula (I) is present in a ratioof at least 1.5a:b (50% excess) or, more specifically, at least 2a:b(100% excess). Similar ratios for any of the lithium material formulasdescribed herein are also contemplated.

In some embodiments, metal precursor comprise alkali metal salts orcomplexes, alkaline earth metal salts or complexes, transition metalsalts or complexes, or the like. In specific embodiments, the fluidstock comprises a lithium precursor and at least one additional metalprecursor, wherein the metal precursor comprises an iron precursor, anickel precursor, a cobalt precursor, a manganese precursor, a vanadiumprecursor, a titanium precursor, a ruthenium precursor, a rheniumprecursor, a platinum precursor, a bismuth precursor, a lead precursor,a copper precursor, an aluminum precursor, a combination thereof, or thelike. In more specific embodiments, the additional metal precursorcomprises an iron precursor, a nickel precursor, a cobalt precursor, amanganese precursor, a vanadium precursor, an aluminum precursor, or acombination thereof. In still more specific embodiments, the additionalmetal precursor comprises an iron precursor, a nickel precursor, acobalt precursor, a manganese precursor, an aluminum precursor, or acombination thereof. In yet more specific embodiments, the additionalmetal precursor comprises a nickel precursor, a cobalt precursor, amanganese precursor, or a combination thereof. In still more specificembodiments, the additional metal precursor comprises at least two metalprecursors from the group consisting of: a nickel precursor, a cobaltprecursor, and a manganese precursor. In more specific embodiments, theadditional metal precursor comprises a nickel precursor, a cobaltprecursor, and a manganese precursor. In specific embodiments, metalprecursors include metal salts or complexes, wherein the metal isassociated with any suitable ligand or radical, or anion or other LewisBase, e.g., a carboxylate (e.g., —OCOCH₃ or another —OCOR group, whereinR is an alkyl, substituted alkyl, aryl, substituted aryl, or the like,such as acetate), an alkoxide (e.g., a methoxide, ethoxide, isopropyloxide, t-butyl oxide, or the like), a halide (e.g., chloride, bromide,or the like), a diketone (e.g., acetylacetone, hexafluoroacetylacetone,or the like), a nitrates, amines (e.g., NR′₃, wherein each R″ isindependently R or H or two R″, taken together form a heterocycle orheteroaryl), and combinations thereof. In specific embodiments, theprecursors are acetates (e.g., lithium acetate).

In some embodiments, (e.g., where metal precursors are utilized, such asa lithium precursor and one or more additional metal precursor) theweight ratio of the metal component(s) (including lithium precursor andadditional metal precursors) to polymer is at least 1:5, at least 1:4,at least 1:3, at least 1:2, at least 1:1, at least 1.25:1, at least1.5:1, at least 1.75:1, at least 2:1, at least 3:1, or at least 4:1. Insome instances, wherein the lithium material is prepared from apreformed lithium-containing-nanoparticle, the nanoparticle to polymerweight ratio is at least 1:5, at least 1:4, at least 1:3, at least 1:2,or the like. In some instances, wherein the metal component of a processdescribed herein comprises a lithium precursor and at least oneadditional metal precursor, the metal component (both lithium andadditional metal precursors) to polymer ratio is at least 1:3, at least1:2, at least 1:1, or the like. In some embodiments, the monomericresidue (i.e., repeat unit) concentration of the polymer in the fluidstock is at least 100 mM. In specific embodiments, the monomeric residue(i.e., repeat unit) concentration of the polymer in the fluid stock isat least 200 mM. In more specific embodiments, the monomeric residue(i.e., repeat unit) concentration of the polymer in the fluid stock isat least 400 mM. In still more specific embodiments, the monomericresidue (i.e., repeat unit) concentration of the polymer in the fluidstock is at least 500 mM. In some embodiments, the fluid stock comprisesat least about 0.5 weight %, at least about 1 weight %, at least about 2weight %, at least about 5 weight %, at least about 10 weight %, atleast about 20 weight %, or at least about 30 weight % polymer.

In some embodiments, a polymer in a process, fluid stock or nanofiberdescribed herein is an organic polymer. In some embodiments, polymersused in the compositions and processes described herein are hydrophilicpolymers, including water-soluble and water swellable polymers. In someaspects, the polymer is soluble in water, meaning that it forms asolution in water. In other embodiments, the polymer is swellable inwater, meaning that upon addition of water to the polymer the polymerincreases its volume up to a limit. Exemplary polymers suitable for thepresent methods include but are not limited to polyvinyl alcohol(“PVA”), polyvinyl acetate (“PVAc”), polyethylene oxide (“PEO”),polyvinyl ether, polyvinyl pyrrolidone, polyglycolic acid,hydroxyethylcellulose (“HEC”), ethylcellulose, cellulose ethers,polyacrylic acid, polyisocyanate, and the like. In some embodiments, thepolymer is isolated from biological material. In some embodiments, thepolymer starch, chitosan, xanthan, agar, guar gum, and the like. Inother instances, e.g., wherein silicon nanoparticles are utilized as thesilicon component, other polymers, such as polyacrylonitrile (“PAN”) areoptionally utilized (e.g., with DMF as a solvent). In other instances, apolyacrylate (e.g., polyalkacrylate, polyacrylic acid,polyalkylalkacrylate, such as poly(methyl methacrylate) (PMMA), or thelike), or polycarbonate is optionally utilized. In some instances, thepolymer is polyacrylonitrile (PAN), polyvinyl alcohol (PVA), apolyethylene oxide (PEO), polyvinylpyridine, polyisoprene (PI),polyimide, polylactic acid (PLA), a polyalkylene oxide, polypropyleneoxide (PPO), polystyrene (PS), a polyarylvinyl, a polyheteroarylvinyl, anylon, a polyacrylate (e.g., poly acrylic acid,polyalkylalkacrylate—such as polymethylmethacrylate (PMMA),polyalkylacrylate, polyalkacrylate), polyacrylamide,polyvinylpyrrolidone (PVP) block, polyacrylonitrile (PAN), polyglycolicacid, hydroxyethylcellulose (HEC), ethylcellulose, cellulose ethers,polyacrylic acid, polyisocyanate, or a combination thereof.

Polymers of any suitable molecular weight may be utilized in theprocesses and nanofibers described herein. In some instances, a suitablepolymer molecular weight is a molecular weight that is suitable forelectrospinning the polymer as a melt or solution (e.g., aqueoussolution or solvent solution—such as in dimethyl formamide (DMF) oralcohol). In some embodiments, the polymer utilized has an averageatomic mass of 1 kDa to 1,000 kDa. In specific embodiments, the polymerutilized has an average atomic mass of 10 kDa to 500 kDa. In morespecific embodiments, the polymer utilized has an average atomic mass of10 kDa to 250 kDa. In still more specific embodiments, the polymerutilized has an average atomic mass of 50 kDa to 200 kDa.

In some embodiments, the polymers described herein (e.g., hydrophilic ornucleophilic polymers) associate (e.g., through ionic, covalent, metalcomplex interactions) with metal precursors described herein whencombined in a fluid stock. Thus, in certain embodiments, provided hereinis a fluid stock that comprises (a) at least one polymer; (b) a lithiumprecursor; and (c) an additional metal precursor (e.g., a metal acetateor metal alkoxide), or is prepared by combining (i) at least onepolymer; (ii) a lithium precursor; and (iii) at least one additionalmetal precursor. In certain embodiments, upon electrospinning of such afluid stock, a nanofiber comprising a polymer associated with the metalprecursors is produced. For example, provided in specific embodimentsherein is a fluid stock comprising PVA in association with a lithiumprecursor and at least one additional metal precursor. In someembodiments, this association is present in a fluid stock or in ananofiber. In specific embodiments, the association having the formula:—(CH₂-CHOM¹)_(n1)-. In specific embodiments, each M is independentlyselected from H, a metal ion, and a metal complex (e.g., a metal halide,a metal carboxylate, a metal alkoxide, a metal diketone, a metalnitrate, a metal amine, or the like).

In further embodiments, provided herein is a polymer (e.g., in a fluidstock or nanofiber) having the following formula: (A_(d)R¹ _(n)-BR¹_(m)R²)_(a). In some embodiments, each of A and B are independentlyselected from C, O, N, or S. In certain embodiments, at least one of Aor B is C. In some embodiments, each R¹ is independently selected fromH, halo, CN, OH, NO₂, NH₂, NH(alkyl) or N(alkyl)(alkyl), SO₂alkyl,CO₂-alkyl, alkyl, heteroalkyl, alkoxy, S-alkyl, cycloalkyl, heterocycle,aryl, or heteroaryl. In certain embodiments, the alkyl, alkoxy, S-alkyl,cycloalkyl, heterocycle, aryl, or heteroaryl is substituted orunsubstituted. In some embodiments, R² is M¹, OM¹, NHM¹, or SM¹, asdescribed above. In specific embodiments, if R¹ or R² is M¹, the A or Bto which it is attached is not C. In some embodiments, any alkyldescribed herein is a lower alkyl, such as a C₁-C₆ or C₁-C₃ alkyl. Incertain embodiments, each R1 or R2 is the same or different. In certainembodiments, d is 1-10, e.g., 1-2. In certain embodiments, n is 0-3(e.g., 1-2) and m is 0-2 (e.g., 0-1). In some embodiments, a is100-1,000,000. In specific embodiments, a substituted group isoptionally substituted with one or more of H, halo, CN, OH, NO₂, NH₂,NH(alkyl) or N(alkyl)(alkyl), SO₂alkyl, CO₂-alkyl, alkyl, heteroalkyl,alkoxy, S-alkyl, cycloalkyl, heterocycle, aryl, or heteroaryl. Incertain embodiments, the block co-polymer is terminated with anysuitable radical, e.g., H, OH, or the like.

In specific embodiments, at least 5% of M¹ are Li⁺. In more specificembodiments, at least 10% of M¹ are Li⁺. In more specific embodiments,at least 15% of M¹ are Li⁺. In still more specific embodiments, at least20% of M¹ are Li⁺. In more specific embodiments, at least 40% of M¹ areLi⁺. In further embodiments, at least 10% of M¹ are a non-lithium metalcomplex (e.g., iron acetate, cobalt acetate, manganese acetate, nickelacetate, aluminum acetate, or a combination thereof). In more specificembodiments, at least 15% of M¹ are non-lithium metal complex. In stillmore specific embodiments, at least 20% of M¹ are non-lithium metalcomplex. In more specific embodiments, at least 40% of M¹ arenon-lithium metal complex. In various embodiments, n1 is any suitablenumber, such as 1,000 to 1,000,000.

In one aspect, described herein is a method for producing an orderedmesoporous nanofiber, the method comprising: (a) coaxiallyelectrospinning a first fluid stock with a second fluid stock to producea first nanofiber, the first fluid stock comprising at least one blockco-polymer and a metal component (e.g., lithium precursor and at leastone additional metal precursor), the second fluid stock comprising acoating agent, and the first nanofiber comprising a first layer (e.g.,core) and a second layer (e.g., coat) that at least partially coats thefirst layer; (b) optionally annealing the first nanofiber; (c)optionally removing the second layer from the first nanofiber to producea second nanofiber comprising the block co-polymer; and (d) thermallyand/or chemically treating the first nanofiber or the second nanofiber(e.g. thereby producing an ordered mesoporous nanofiber). In specificembodiments, the block copolymer orders itself upon annealing, with themetal component preferentially going into one phase (e.g., a hydrophilicphase of the copolymer)—and, upon thermal treatment (e.g., calcinationof precursor), a mesoporous lithium material is produced. Additionalcoaxial layers are optional—e.g., comprising a precursor and blockcopolymer for an additional mesoporous layer, or a precursor and apolymer as described herein for a non-mesoporous layer.

In some embodiments, the block co-polymer comprises a polyisoprene (PI)block, a polylactic acid (PLA) block, a polyvinyl alcohol (PVA) block, apolyethylene oxide (PEO) block, a polyvinylpyrrolidone (PVP) block,polyacrylamide (PAA) block or any combination thereof (i.e., thermallyor chemically degradable polymers). In some embodiments, the blockco-polymer comprises a polystyrene (PS) block, a poly(methylmethacrylate) (PMMA) block, a polyacrylonitrile (PAN) block, or anycombination thereof. In some embodiments, the coating layer and at leastpart of the block co-polymer (concurrently or sequentially) isselectively removed in any suitable manner, such as, by heating, byozonolysis, by treating with an acid, by treating with a base, bytreating with water, by combined assembly by soft and hard (CASH)chemistries, or any combination thereof. Additionally, U.S. applicationSer. No. 61/599,541 and International Application Ser. No.PCT/US13/26060, filed Feb. 14, 2013 are incorporated herein by referencefor disclosures related to such techniques.

In some embodiments, the fluid stock further comprises a calcinationreagent. In certain embodiments, the calcination reagent is a phosphorusreagent (e.g., for preparing lithium metal phosphates or phosphides uponthermal treatment/calcination of a nanofiber spun from a fluid stockcomprising lithium and at least one additional metal precursors), asilicon reagent (e.g., for preparing lithium metal silicates uponthermal treatment/calcination of a nanofiber spun from a fluid stockcomprising lithium and at least one additional metal precursors), asulfur reagent (e.g., for preparing lithium metal sulfides or sulfatesupon thermal treatment/calcination of a nanofiber spun from a fluidstock comprising lithium and at least one additional metal precursors),or a boron reagent (e.g., for preparing lithium metal borates uponthermal treatment/calcination of a nanofiber spun from a fluid stockcomprising lithium and at least one additional metal precursors). Insome embodiments, the reagent is elemental material (e.g., phosphorus,sulfur) or any other suitable chemical compound. In some embodiments,the calcination reagent has the formula: X¹R¹ _(q), wherein X¹ is anon-metal (or metalloid), such as S, P, N, B, Si, or Se; each R¹ isindependently H, halo, CN, OH (or O—), NO₂, NH₂, —NH(alkyl) or—N(alkyl)(alkyl), —SO₂alkyl, —CO₂-alkyl, alkyl, heteroalkyl, alkoxy,—S-alkyl, cycloalkyl, heterocycle, aryl, heteroaryl, oxide (=O); and qis 0-10 (e.g., 0-4). In certain embodiments, the alkyl, alkoxy, S-alkyl,cycloalkyl, heterocycle, aryl, or heteroaryl is substituted orunsubstituted. In specific embodiments, q is 0. In some embodiments, R1is alkoxy (e.g., wherein the calcination reagent is triethylphosphite).In some embodiments wherein metal oxides are prepared, an oxygen reagentis air, which is provided in the atmosphere (e.g., which can react uponsufficient thermal conditions with the metal precursors or calcinedmetals). In certain embodiments, wherein metal carbides are prepared, acarbon reagent (or carbon source) is the organic polymer material (e.g.,which can react upon sufficient thermal conditions with the metalprecursor(s)).

Electrospinning

In some embodiments, the process comprises electrospinning a fluidstock. Any suitable method for electrospinning is used.

In some instances, elevated temperature electrospinning is utilized.Exemplary methods for comprise methods for electrospinning at elevatedtemperatures as disclosed in U.S. Pat. No. 7,326,043 and U.S. Pat. No.7,901,610, which are incorporated herein for such disclosure. In someembodiments, elevated temperature electrospinning improves thehomogeneity of the fluid stock throughout the electrospinning process.

In some embodiments, gas assisted electrospinning is utilized (e.g.,about a common axis with the jet electrospun from a fluid stockdescribed herein). Exemplary methods of gas-assisted electrospinning aredescribed in PCT Patent Application PCT/US2011/024894 (“Electrospinningapparatus and nanofibers produced therefrom”), which is incorporatedherein for such disclosure. In gas-assisted embodiments, the gas isoptionally air or any other suitable gas (such as an inert gas,oxidizing gas, or reducing gas). In some embodiments, gas assistanceincreases the throughput of the process and/or reduces the diameter ofthe nanofibers. In some instances, gas assisted electrospinningaccelerates and elongates the jet of fluid stock emanating from theelectrospinner. In some instances, gas assisted electrospinningdisperses nanoparticles in nanocomposite nanofibers. For example, insome instances, gas assisted electrospinning (e.g., coaxialelectrospinning of a gas along a substantially common axis—with a fluidstock comprising lithium containing nanoparticles) facilitatesdispersion or non-aggregation of the Li containing nanoparticles in theelectrospun jet and the resulting as-spun nanofiber (and subsequentnanofibers produced therefrom). In some embodiments, incorporating a gasstream inside a fluid stock produces hollow nanofibers. In someembodiments, the fluid stock is electrospun using any suitabletechnique.

In specific embodiments, the process comprises coaxial electrospinning(electrospinning two or more fluids about a common axis). As describedherein, coaxial electrospinning a first fluid stock as described hereinwith a second fluid is used to add coatings, make hollow nanofibers,make nanofibers comprising more than one material, and the like. Invarious embodiments, the second fluid is either outside (i.e., at leastpartially surrounding) or inside (e.g., at least partially surroundedby) the first fluid stock. In some embodiments, the second fluid is agas (gas-assisted electrospinning) In some embodiments, gas assistanceincreases the throughput of the process, reduces the diameter of thenanofibers, and/or is used to produce hollow nanofibers. In someembodiments, the method for producing nanofibers comprises coaxiallyelectrospinning the first fluid stock and a gas. In other embodiments,the second fluid is a second fluid stock and comprises a polymer and anoptional metal component (e.g., a silicon and/or non-silicon metalcomponent).

In some embodiments, the nanofibers comprise a core material. In someembodiments, the core material is highly conductive. In someembodiments, the highly conductive material is a metal. In one aspect,described herein are methods for producing nanofibers, the nanofiberscomprising a core material, optionally a highly conductive corematerial, optionally a metal core. In some embodiments, lithiumnanoparticles are embedded within the core material/matrix.

Thermal/Chemical Treatment

The heating step performs any suitable function. In some embodiments,the heating step carbonizes the polymer. In some embodiments, theheating step removes the polymer. In some embodiments, the heating stepselectively removes a polymer phase. In some embodiments, removing(e.g., selectively) the polymer and/or polymer phase results in porousnanofibers. In some embodiments, the heating step calcines and/orcrystallizes the precursors. In certain embodiments, the heating stepcalcines and/or crystallizes the precursors and/or nanoparticles. Insome embodiments, the heating step determines the oxidation state of thehigh energy capacity material, precursors thereof and/or nanoparticlesthereof, or any combination thereof.

In some embodiments, the nanofibers are heated in oxidative (e.g., inair atmosphere), inert (e.g., under argon or nitrogen), or reductiveconditions (e.g., under hydrogen or inert gas/hydrogen mixtures). Inspecific embodiments, thermal treatment occurs in the presence of air,nitrogen, nitrogen/H₂ (e.g., 95%/5%), argon, argon/H₂ (e.g., 96%/4%), orany combination thereof.

Alternatively, in some instances certain chemical reactions occur uponheating, optionally oxidation reactions. In some embodiments, exposureto (e.g., concurrent with thermal treatment) oxidative conditionsconvert metal precursors to metal oxide or ceramic. In certainembodiments, exposure to (e.g., concurrent with thermal treatment)oxidative conditions convert metal (e.g., metal prepared by calcinationof metal precursor to metal under inert or inert/reductive conditions)to metal oxide or ceramic. In some embodiments, oxidative conditions areperformed in an oxygen-rich environment, such as air. In one particularexample where the nanofiber is a ceramic nanofiber, calcination isperformed in air at about 600° C. for about 2 hours.

Thermal and/or chemical treatments are performed at any suitabletemperature and for any suitable time. In some instances, highertemperature treatments produce nanofibers of a smaller diameter.

In some embodiments, thermal treatment is performed at about 100° C.,about 150° C., about 200° C., about 300° C., about 400° C., about 500°C., about 600° C., about 700° C., about 800° C., about 900° C., about1,000° C., about 1,500° C., about 2,000° C., and the like. In someembodiments, thermal treatment is performed at a temperature of at least100° C., at least 150° C., at least 200° C., at least 300° C., at least400° C., at least 500° C., at least 600° C., at least 700° C., at least800° C., at least 900° C., at least 1,000° C., at least 1,500° C., atleast 2,000° C., and the like. In some embodiments, heating is performedat a temperature of at most 100° C., at most 150° C., at most 200° C.,at most 300° C., at most 400° C., at most 500° C., at most 600° C., atmost 700° C., at most 800° C., at most 900° C., at most 1,000° C., atmost 1,500° C., at most 2,000° C., and the like. In some embodiments,heating is performed at a temperature of between about 300° C. and 800°C., between about 400° C. and 700° C., between about 500° C. and 900°C., between about 700° C. and 900° C., between about 800° C. and 1,200°C., and the like.

Heating is performed at a constant temperature, or the temperature ischanged over time. In some embodiments, the rate of temperature increaseis between about 0.1° C./min and 10° C./min, between about 0.5° C./minand 2° C./min, between about 2° C./min and 10° C./min, between about0.1° C./min and 2° C./min, or the like.

Heating is performed for any suitable amount of time necessary to arriveat a nanofiber with the desired properties. In some embodiments, heatingis performed for at least 5 minutes, at least 15 minutes, at least 30minutes, at least 1 hour, at least 2 hours, at least 3 hours, at least 4hours, at least 8 hours, at least 12 hours, at least 1 day, at least 2days, and the like.

System

In one aspect, described herein is a lithium ion battery system, thesystem comprising: (a) an electrolyte; (b) an anode in a first chamber;(c) a cathode in a second chamber, the cathode comprising a plurality oflithium containing nanofibers; and (d) a separator between the firstchamber and the second chamber, and the separator allowing lithium iontransport between the first chamber and second chamber (e.g., in atemperature dependent manner).

In one aspect, described herein is a system for producing nanofibers fora lithium ion battery, the system comprising: (a) a fluid stockcomprising a polymer and inorganic precursors or nanoparticles; (b) anelectrospinner suitable for electrospinning the fluid stock intonanofibers; (c) a heater suitable for heating the nanofibers; and (d)optionally a module suitable for contacting the nanofibers with an acid.

In some embodiments, electrospinning (e.g., with an aid of gas stream)allows for the high throughput generation of nanomaterials with theability to control this crystal structure. In some embodiments, purelyinorganic or organic/inorganic hybrid nanofibers are generated byinclusion of various metal/ceramic precursors (metal nitrate, acetate,acetylacetonate, etc.) or preformed nanoparticles (e.g., a lithiummaterial described herein) within a polymer (PVA, PAN, PEO, etc.)solution, as shown in the schematic in FIG. 1. In some embodiments,thermal treatment is used to carbonize polymers, remove polymers,selectively remove a single polymer phase, and/or crystallize and/orcalcine included precursors or nanoparticles with controlled oxidationstate. In some embodiments, porosity in the nanofibers is controlled bythe removal of a polymer domain during thermal treatment, asdemonstrated in FIG. 3 for porous LiCoO₂ nanofiber for cathodeapplication. In some instances, this allows for greater surface area tovolume ratio and/or greater electrolyte contact increasing ion transfer,while accommodating volume expansion during lithiation and de-lithiationprocesses.

FIG. 1 illustrates a process according to certain embodiments describedherein. In some embodiments, a fluid stock 1003 is prepared by preparingby combining 1002 a fluid (e.g., water, alcohol, or dimethylformamide(DMF)), a polymer and a lithium component 1001 (e.g., lithium precursorsand additional metal precursor(s) and/or lithium containingnanoparticles). In some embodiments, a homogenous fluid stock with aviscosity suitable for electrospinning is prepared 1004 by heatingand/or mixing the combination. In certain embodiments, the fluid stockis then electrospun from a needle apparatus 1006 (optionally via gasassisted, such as coaxially gas assisted, electrospinning), e.g., usinga syringe 1005. In some embodiments, the nanofibers 1008 are collectedon a collector 1007 and optionally thermally treated 1009 to providelithium-containing nanofibers 1010 described herein. In someembodiments, thermal treatment of the as-spun nanofibers carbonizesand/or removes (e.g., via carbonization and subsequent conversion toCO₂). In further or alternative embodiments, thermal treatment calcinesmetal precursor materials to provide a metal component (e.g., metals,metal oxides, metal phosphates, metal sulfides, metal silicates, metalborates, or the like (e.g., depending on what, if any, calcinationreagents are utilized)). In some embodiments, calcination of the metalprecursors provides a crystalline metal component (e.g., metal, metaloxide, etc.).

Certain Definitions

The articles “a”, “an” and “the” are non-limiting. For example, “themethod” includes the broadest definition of the meaning of the phrase,which can be more than one method.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

EXAMPLES Example 1 Nanofiber Having a Continuous Core Matrix of aLithium (Metal Oxide)-Containing-Material

A first composition is prepared by combining 0.5 g PVA (79 kDa, 88%hydrolyzed) with 4.5 g water. The first composition is heated to 95 Cfor at least 8 hours. A second composition is prepared by combining 1 gwater, 0.5 g acetic acid, 3 drops x-100 surfactant, lithium acetate(hydrate) and one or more metal precursor (e.g., cobalt acetate(hydrate), manganese acetate (hydrate), nickel acetate (hydrate)). Thesecond composition is mixed for at least 4 hours. The first and secondcompositions are combined and mixed for at least 2 hours to form a fluidstock.

The fluid stock is electrospun in a coaxial gas assisted manner, using aflow rate of 0.01 mL/min, a voltage of 20 kV and a tip to collectordistance of 15 cm. The fluid stock is also electrospun without coaxialgas assistance, using a flow rate of 0.005 mL/min, a voltage of 20 kVand a tip to collector distance of 18 cm. Electrospinning of the fluidstock prepares an as-spun precursor nanofiber, which is subsequentlythermally treated.

A one step thermal treatment procedure involves treating the as-spunnanofibers in air at about 700 C (with a heat/cool rate of 2 C/min) for5 hours. A two step thermal treatment procedure involves a first thermaltreatment under argon at about 700 C (with a heat/cool rate of 2 C/min)for 5 hours, and a second thermal treatment under air at about 500 C(with a heat/cool rate of 2 C/min).

For all examples, X-Ray diffraction (XRD) done using Scintag 2-thetadiffractometer; scanning electron microscopy (SEM) with Leica 440 SEM;transmission electron microscopy (TEM) with FEI Spirit TEM.

Example 2 LiCoO₂ Nanofibers

Using a gas assisted procedure of Example 1, wherein cobalt acetate isutilized as the metal precursor, lithium cobalt oxide nanofibers areprepared. Nanofibers are prepared using 1:1, 1:1.5, and 1:2 molar ratiosof cobalt acetate-to-lithium acetate.

FIG. 2 illustrates an SEM image of such nanofibers (panel A). FIG. 2(panel B) also illustrates SEM images such nanofibers prepared using1:1, 1:1.5, and 1:2 molar ratios of cobalt acetate-to-lithium acetate(ratios in the figure are inverted). FIG. 3 (panel A) illustrates theXRD pattern for the lithium cobalt oxide nanofibers and illustrates theXRD pattern (panel B) for nanofibers prepared using 1:1, 1:1.5, and 1:2molar ratios of cobalt acetate-to-lithium acetate (ratios in the figureare inverted). FIG. 4 illustrates the charge/discharge capacities forlithium cobalt oxide prepared using a one step thermal process (panel A)and a two step thermal process (panel B). The lithium cobalt oxidenanofibers produced is observed to have an initial capacity of about 120mAh/g at 0.1 C.

Table 1 illustrates charge capacities determined using the variouslithium-metal ratios and the one and two step thermal treatmentprocesses.

TABLE 1 Li:Co Thermal Charge capacity (ratio for stock) Treatment(mAh/g) 1:1 700 C./air N/A 1.5:1  700 C./air 67 2:1 700 C./air 89 2:1 1.700 C./Ar 50 2. 300 C./air 2:1 1. 700 C./Ar 110  2. 700 C./air

Example 3 Li(Ni_(x)Co_(y)Mn_(z))O₂ Nanofibers

Using a gas assisted procedure of Example 1, wherein nickel acetate,cobalt acetate, and manganese acetate are utilized as the metalprecursor, Li_(a)(Ni_(x)Co_(y)Mn_(z))O₂ nanofibers are prepared.Nanofibers are prepared using 1:1, 1:1.5, and 1:2 molar ratios of thecombined nickel/cobalt/manganese acetate-to-lithium acetate. Variousmolar ratios of nickel acetate (x) to cobalt acetate (y) to manganeseacetate (z) are utilized

FIG. 5 (panel A) illustrates an SEM image of as-spun nanofibers preparedusing a 1:1:1 ratio of x:y:z. Panel B illustrates an SEM image ofthermally treated (Li(Ni_(1/3)Co_(1/3)Mn_(1/3))O₂) nanofibers (treatedat 650 C in air). Panel C illustrates a TEM image of the thermallytreated nanofibers. FIG. 6 illustrates the XRD pattern for the thermallytreated nanofibers. FIG. 7 illustrates the charge/discharge capacitiesfor 1:1:1 (x:y:z) nanofibers prepared. The nanofibers produced isobserved to have an initial capacity of about 180 mAh/g at 0.1 C.

Using similar procedures, Li[Li_(0.2)Mn_(0.56)Ni_(0.16) Co_(0.08)]O₂nanofibers are also prepared. FIG. 8 illustrates the as-spun andthermally treated (900 C for 5 hours under argon) nanofibers. FIG. 9illustrates the charge/discharge capacities for nanofibers prepared. Thenanofibers produced is observed to have an initial capacity of about 90mAh/g at 0.1 C.

Using similar procedures, Li_(0.8)Mn_(0.4)Ni_(0.4)Co_(0.4)O₂ nanofibersare prepared. FIG. 10 (panel A) illustrates as-spun nanofibers and(panel B) thermally treated (900 C for 5 hours under argon) nanofibers.

Example 4 LiMn₂O₄ Nanofibers

Using a gas assisted procedure of Example 1, wherein manganese acetateis utilized as the metal precursor, LiMn₂O₄ nanofibers are prepared.Nanofibers are prepared using 2:1, 3:2 (50% excess lithium acetate), and1:1 (100% excess lithium acetate) molar ratios of the manganeseacetate-to-lithium acetate.

FIG. 11 (panel A) illustrates an SEM image of as-spun nanofibers. PanelB illustrates an SEM image of thermally treated nanofibers (treated at650 C in air). Panel C illustrates a TEM image of the thermally treatednanofibers. FIG. 12 illustrates the XRD pattern for the thermallytreated nanofibers. FIG. 13 illustrates the charge/discharge capacity ofthe nanofibers for about 40 cycles. The lithium manganese oxidenanofibers produced is observed to have an initial capacity of about 95mAh/g at 0.1 C.

Example 5 Li(Ni_(x)Mn_(z))O₄ Nanofibers

Using a gas assisted procedure of Example 1, wherein nickel acetate andmanganese acetate are utilized as the metal precursor,Li(Ni_(x)Mn_(z))O₄ nanofibers are prepared. Nanofibers are preparedusing 2:1, 3:2, and 1:1 molar ratios of the combined nickel/manganeseacetate-to-lithium acetate. Various molar ratios of nickel acetate (x)to manganese acetate (z) are utilized (e.g., 1:3 forLi(Ni_(0.5)Mn_(1.5))O₄). FIG. 14 illustrates the XRD pattern for thethermally treated nanofibers.

Example 6 Nanofiber Having a Continuous Core Matrix of a Lithium (MetalPhosphate)-Containing-Material

A first composition is prepared by combining 0.5 g PVA (79 kDa, 88%hydrolyzed) with 4.5 g water. The first composition is heated to 95 Cfor at least 8 hours. A second composition is prepared by combining 1 gwater, 0.5 g acetic acid, 3 drops x-100 surfactant, lithium acetate(hydrate), one or more metal precursor (e.g., iron acetate (hydrate),cobalt acetate (hydrate), manganese acetate (hydrate), nickel acetate(hydrate)), and a phosphorus precursor (e.g., triethylphosphite). Thesecond composition is mixed for at least 4 hours. The first and secondcompositions are combined and mixed for at least 2 hours to form a fluidstock.

The fluid stock is electrospun in a coaxial gas assisted manner, using aflow rate of 0.01 mL/min, a voltage of 20 kV and a tip to collectordistance of 15 cm. The fluid stock is also electrospun without coaxialgas assistance, using a flow rate of 0.005 mL/min, a voltage of 20 kVand a tip to collector distance of 18 cm. Electrospinning of the fluidstock prepares an as-spun precursor nanofiber, which is subsequentlythermally treated.

A one step thermal treatment procedure involves treating the as-spunnanofibers in air at about 700 C (with a heat/cool rate of 2 C/min) for5 hours. A two step thermal treatment procedure involves a first thermaltreatment under argon at about 700 C (with a heat/cool rate of 2 C/min)for 5 hours, and a second thermal treatment under air at about 500 C(with a heat/cool rate of 2 C/min).

Example 7 LiFePO₄ Nanofibers

Using a gas assisted procedure of Example 6, wherein iron acetate isutilized as the metal precursor, lithium iron phosphate nanofibers areprepared. Nanofibers are prepared using 1:1, 1:1.5, and 1:2 molar ratiosof iron acetate-to-lithium acetate.

FIG. 15 illustrates an SEM image of the as-spun nanofibers (panel A) andthermally treated nanofibers (panel B). FIG. 16 illustrates the XRDpattern for the lithium iron phosphate nanofibers.

Example 8 Nanofiber Having a Continuous Core Matrix of a Lithium(Sulfide/Sulfate)-Containing-Material

A first composition is prepared by combining 0.5 g PVA (79 kDa, 88%hydrolyzed) with 4.5 g water. The first composition is heated to 95 Cfor at least 8 hours. A second composition is prepared by combining 1 gwater, 0.5 g acetic acid, 3 drops x-100 surfactant, lithium acetate(hydrate), and a sulfur precursor (e.g., elemental sulfur, such assulfur nanoparticles). The second composition is mixed for at least 4hours. The first and second compositions are combined and mixed for atleast 2 hours to form a fluid stock.

The fluid stock is electrospun in a coaxial gas assisted manner, using aflow rate of 0.01 mL/min, a voltage of 20 kV and a tip to collectordistance of 15 cm. The fluid stock is also electrospun without coaxialgas assistance, using a flow rate of 0.005 mL/min, a voltage of 20 kVand a tip to collector distance of 18 cm. Electrospinning of the fluidstock prepares an as-spun precursor nanofiber, which is subsequentlythermally treated.

The thermal treatment occurs under argon at about 1000 C (with aheat/cool rate of 2 C/min) for 5 hours for preparation of lithiumsulfide containing fibers (Li₂S/Carbon nanocomposites). Subsequent airoxidation provides lithium sulfate containing fibers (Li₂SO₄/Carbonnanocomposites). FIG. 17 illustrates an SEM image of the as-spunnanofibers (panel A) and thermally treated nanofibers (panel B). Panel Cillustrates a TEM image of the thermally treated nanofibers. FIG. 18illustrates the XRD pattern for the oxidized nanofibers.

For fabricating the half cells, Li metal is used as a counter electrodeand polyethylene (ca. 25 μm thickness) is inserted as a separatorbetween working electrode and counter electrode. The mass of workingelectrode is 3˜4 mg/cm². The coin cell-typed Li-ion batteries areassembled in Ar-filled glove box with electrolyte. The cut off voltageduring the galvanostatic tests is 0.01˜2.0 V for anode and 2.5˜4.2 V byusing battery charge/discharge cyclers from MTI.

We claim: 1-43. (canceled)
 44. A process for producing a nanofibercomprising a backbone of a lithium-containing-material, the processcomprising: gas-assisted electrospinning a fluid stock to produce ananofiber, the fluid stock comprising a combination of (i) polymer, (ii)lithium salt, and (iii) nickel precursor, cobalt precursor, manganeseprecursor, or a combination thereof; thermally treating the nanofiberunder oxidative conditions at a temperature of at least 300° C. toproduce the lithium-containing nanofiber; thelithium-containing-material having formula (I):Li_(a)M_(b)X_(c)   (I) wherein M is Ni, Co, Mn, or a combinationthereof; X is O; a is 1-2; b is 0-2; and c is 1-4.
 45. The process ofclaim 44, wherein the polymer is polyacrylonitrile (PAN), polyvinylalcohol (PVA), polyvinyl pyrrolidone (PVP), or a combination thereof.46. The process of claim 44, wherein the fluid stock is aqueous.
 47. Theprocess of claim 44, wherein the combined concentration of lithium saltand metal precursor is present in or provided into the fluid stock in aconcentration of at least 200 mM.
 48. The process of claim 44, whereinthe polymer comprises a plurality of repeating monomeric residues, andthe combined lithium salt and metal precursor being combined with thepolymer in a precursor-to-monomeric residue ratio of at least 1:4. 49.The process of claim 44, wherein the fluid stock comprises a combinationof nickel precursor, cobalt precursor, and manganese precursor.
 50. Theprocess of claim 44, wherein the fluid stock comprises a combination ofnickel precursor, cobalt precursor, and manganese precursor in a molarratio of about 1:1:1.
 51. The process of claim 44, wherein the fluidstock comprises a combination of lithium salt and metal precursor in aratio of about a:b.
 52. The process of claim 44, wherein the fluid stockcomprises a combination of lithium salt and metal precursor in a ratioof >a:b.
 53. A nanofiber comprising a backbone of alithium-containing-material, the lithium-containing-material having theformula (I):Li_(a)M_(b)X_(c)   (I) wherein M is Ni, Co, Mn, or a combination thereofX is O; a is 1-2; b is 0-2; and c is 1-2.
 54. The nanofiber of claim 53,wherein a is 1 and b is
 1. 55. The nanofiber of claim 53, wherein M is(Ni_(1/3)Co_(1/3)Mn_(1/3)).
 56. The nanofiber claim 53, wherein thelithium-containing-material comprises at least 80 wt. % of thenanofiber.
 57. The nanofiber of claim 53, wherein the nanofibercomprises at least 2.5 wt. % lithium.
 58. The nanofiber of claim 53,wherein at least 10% of the atoms present in the nanofiber are lithiumatoms.
 59. The nanofiber of claim 53, having an initial capacity of atleast 100 mAh/g as a cathode in a lithium ion battery at acharge/discharge rate of 0.1 C.
 60. The nanofiber of claim 53, having adiameter of less than 1 micron, and a specific surface are of at least10 m²/g.
 61. A composition comprising a combination of polymer and metalprecursor; the metal precursor comprising lithium salt, nickelprecursor, cobalt precursor, and manganese precursor; the polymer beingpolyvinylalcohol (PVA), polyacrylonitrile (PAN), or polyvinylpyrrolidone (PVP); and the metal precursor being combined with thepolymer in a metal precursor-to-polymer weight ratio of at least 1:4.62. The composition of claim 61, wherein the metal precursor-to-polymerweight ratio is at least 1:2.
 63. The composition of claim 61, whereinthe composition is a fluid and the combined concentration of the metalprecursor is at least 200 mM.